Community-level diversity modelling of birds and butterflies on Anjouan, Comoro Islands     

Charles J. Marsh  Owen T. Lewis  Robert M. Ewers 《Biological conservation》2010,143(6):1364-1374

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Implications derived from a mathematical model for eradication of pseudorabies virus     

A. Van Nes  M. C. M. De Jong  J. A. A. M. Buijtels  J. H. M. Verheijden 《Preventive veterinary medicine》1998,33(1-4):39-58

Simple mathematical models based on experimental and observational data were applied to evaluate the feasibility of eradicating pseudorabies virus (PRV) regionally by vaccination and to determine which factors can jeopardise eradication. As much as possible, the models were uncomplicated and our conclusions were based on mathematical analysis. For complicated situations, Monte-Carlo simulation was used to support the conclusions. For eradication, it is sufficient that the reproduction ratio R (the number of units infected by one infectious unit) is < 1. However, R can be determined at different scales: at one end the region with the herds as units and at the other end compartments with the pigs as units. Results from modelling within herds showed that contacts between groups within a herd is important whenever R between individuals (R_ind) is 1 in one or more groups. This is the case within finishing herds. In addition, if the R_ind is more than 1 within a herd, the size of the herd determines whether PRV can persist in the herd and determines the duration of persistence. Moreover, when reactivation of PRV in well-vaccinated sows is taken into account, R_ind in sow herds is still less than 1. In sow herds with group-housing systems, it is possible that in those groups R_ind is 1. Results from modelling between herds showed that whether or not R_herd is < 1 in a particular region is determined by two factors: (1) the transmission of infection between nucleus herds and rearing herds through transfer of animals and (2) contacts among finishing herds and among rearing herds. The transmission between herds can be reduced by reduction of the contact rate between herds, reduction of the herd size, and reduction of the transmission within herds.  相似文献   

Detection of resistance-associated point mutations of organophosphate-insensitive acetylcholinesterase in the olive fruit fly, Bactrocera oleae (Gmelin)     

Nicola J. Hawkes  Robert W. Janes  John Vontas 《Pesticide biochemistry and physiology》2005,81(3):154-163

We have recently identified two resistance-associated point mutations of organophosphate (OP)-insensitive acetylcholinesterase in the olive fruit fly Bactrocera oleae, the most important olive orchard pest world-wide. We have developed simple PCR-restriction fragment length polymorphism assays for each mutation, utilising an AccI restriction site created by Ile214Val, and a BssHII restriction site destroyed by a neutral change always accompanying the second mutation Gly488Ser. Samples from Greece homozygous for both mutations proved the most insensitive to dimethoate. The frequencies of these mutations in field-collected samples from several countries were investigated. Ninety-three percent of samples from Greece and Albania, where OPs have been extensively used in B. oleae control, were homozygous for both mutations. Resistance-associated alleles were detected at lower frequencies, but still with both mutations in conjunction in the majority of cases, in western Mediterranean countries with limited use of OPs. Samples from South Africa, however, did not have either of the resistance-associated mutations. The double mutation haplotype clearly confers a strong selective advantage in field populations of B. oleae exposed to OPs.  相似文献   

Chemical time bombs from landfills: Appraisal and modelling     

D. Boels  G. Fleming 《Land Degradation \u0026amp; Development》1993,4(4):399-405

About 240 x 106 tonnes of industrial waste, 104 x 106 tonnes of municipal waste and more than 60 x 106 tonnes of sediment sludge are landfilled (65 per cent), incinerated (24 per cent) and partly recycled in Europe annually. About 60000-120000 landfill sites, occupying 800-1700 km2, are recorded in the EEC, of which a limited number are in operation. These sites generate 12.5 x 109 m3 of landfill gas annually, of which about 755 x 106 m3 are presently recovered, and 0-1-4-0 x 106 m3 of heavily polluted leachate, which is dispersed to ground and surface waters. the area with polluted groundwater increases annually by 1-10 per cent (1200-12000 km2 of contaminated land). Landfill gas contains carcinogenic and pathogenic components and contributes 2 per cent of the total emission of greenhouse gases; locally it is a potential hazard. Incinerators reduce the solid volume to about 30 per cent of the original but cause the atmospheric deposition of acids and dioxins. Emissions of landfill gas, leachate and atmospheric deposition have been recognized as potential chemical time bombs (CTBs). Models are currently available for the estimation of the time at which the effects of these CTBs will become manifest. It is recommended that an inventory of all landfills should be made to assess the potential hazards in detail, to encourage institutions to initiate the clean-up of contaminated sites and the aftercare of closed sites, and to set up a co-operative network within the EEC.  相似文献   

浙江地区竹编工艺特色概述   总被引：2，自引：0，他引：2  

吴婕妤  陈红  费本华  马欣欣  张露文 《林产工业》2020,57(3):61-64

介绍了浙江地区特别是嵊州和东阳两地独特的竹编工艺,包括竹编编织技法、选材特点、造型用色等,并对竹编工艺的发展提出建议。  相似文献   

论加权回归与建模   总被引：44，自引：2，他引：44  

曾伟生  骆期邦  贺东北 《林业科学》1999,35(5):5-11

以加权回归估计方法为核心,对林业上常用的模型的异方差性进行了研究,提出了能彻底消除异方差的最佳权函数,并对模型的评价指标进行了探讨,提出了评价通用性回归模型的３大指标,并分析了加权回归估计与这些评价指标之间的关系,最后对样本资料的收集进行了讨论,提出了收集建模样本应遵循的基本原则。  相似文献   

Impact of agricultural subsidies on biodiversity at the landscape level   总被引：1，自引：0，他引：1  

Thomas K. Gottschalk  Tim Diekötter  Klemens Ekschmitt  Bernd Weinmann  Friedrich Kuhlmann  Tobias Purtauf  Jens Dauber  Volkmar Wolters 《Landscape Ecology》2007,22(5):643-656

Agricultural management is a major factor driving the change of faunal richness in anthropogenic landscapes. Thus, there is an urgent need to develop tools that allow decision-makers to understand better intended and unintended effects of agricultural policy measures on biodiversity. Here we demonstrate the potential of such a tool by combining a socio-economic model with the biodiversity model GEPARD to forecast the response of bird and carabid species richness to two scenarios of agricultural subsidies: (1) subsidies based on production levels and prices and (2) direct income support that is independent of production levels. We focussed on farmland of the Lahn-Dill area, Germany, as an example of European regions with low intensity farming. GEPARD predicts faunal richness and is based on multi-scaled resource-selection functions. Under both scenarios the area of predicted losses in species richness of birds and carabids was larger than the area of predicted gains in species richness. However, the area with predicted losses of avian richness was smaller under the direct income support scenario than under the production-based subsidy scenario, whereas the area with predicted losses of carabid species richness was smaller under the production-based subsidy scenario than under the direct income support. Yet locally, richness gains of up to four species were predicted for carabids under both scenarios. We conclude that the sometimes contrasting and heterogeneous responses of birds and carabids at different localities suggest the need for spatially targeted subsidy schemes. With the help of the GIS-based approach presented in this study, prediction maps on potential changes in local and regional species richness can be easily generated.  相似文献   

Risk of introduction of BSE into Japan by the historical importation of cattle from the United Kingdom and Germany   总被引：1，自引：0，他引：1  

Sugiura K 《Preventive veterinary medicine》2004,64(2-4):191-200

All cattle of UK and German origin imported to Japan since 1980 and slaughtered before 2002 were traced (n = 33 and 15 respectively) and the probability that none, one, two or three of these imported cattle had developed BSE (reached the end or last stage of incubation period) at the year of slaughter/death was calculated. The predicted risk that BSE was introduced into Japan by imported cattle was 0.18. Among cattle imported from these countries in various years, cattle imported from the UK in 1987 and 1988 presented the highest risk, while the risk that BSE entered Japan by live cattle imported from the UK in 1982 and from Germany in 1993 was negligible. Because there was no effective system to avoid the recycling of the BSE agent, those infected cattle imported from the UK in 1987 and 1988 most probably entered the feed chain in Japan in 1992 and 1993.  相似文献   

Inferences about the transmission of Schmallenberg virus within and between farms     

Simon Gubbins  Joanne Turner  Matthew Baylis  Yves van der Stede  Gerdien van Schaik  José Cortiñas Abrahantes  Anthony J. Wilson 《Preventive veterinary medicine》2014

In the summer of 2011 Schmallenberg virus (SBV), a Culicoides-borne orthobunyavirus, emerged in Germany and The Netherlands and subsequently spread across much of Europe. To draw inferences about the transmission of SBV we have developed two models to describe its spread within and between farms. The within-farm model was fitted to seroprevalence data for cattle and sheep farms in Belgium and The Netherlands, with parameters estimated using approximate Bayesian computation. Despite the short duration of viraemia in cattle and sheep (mean of 3–4 days) the within-farm seroprevalence can reach high levels (mean within-herd seroprevalence >80%), largely because the probability of transmission from host to vector is high (14%) and SBV is able to replicate quickly (0.03 per day-degree) and at relatively low temperatures (threshold for replication: 12.3 °C). Parameter estimates from the within-farm model were then used in a separate between-farm model to simulate the regional spread of SBV. This showed that the rapid spread of SBV at a regional level is primarily a consequence of the high probability of transmission from host to vector and the temperature requirements for virus replication. Our results, obtained for a region of the UK in a typical year with regard to animal movements, indicate that there is no need to invoke additional transmission mechanisms to explain the observed patterns of rapid spread of SBV in Europe. Moreover, the imposition of movement restrictions, even a total movement ban, has little effect on the spread of SBV at this scale.  相似文献   

Neural network modelling of flat-plate solar collectors     

I. Farkas  P. Gczy-Víg 《Computers and Electronics in Agriculture》2003,40(1-3):87

In this study, different approaches to the modelling of flat-plate solar collectors are introduced and analysed. Among the physically based models, the heat network model and Hottel–Vhillier (H–V) models are discussed. The parameters of the latter model are identified for three different types of these solar collectors. The identification exhibited good agreement with the measured values. Finally, modelling simulations with an artificial neural network (ANN) technique were carried out. A sensitivity study was performed on the parameters of the neural network. The possible ANN structures, the size of training data set, the number of hidden neurons, and the type of training algorithm were analysed in order to identify the most appropriate model. The same ANN structures were trained and validated for the three solar collectors, using data generated from the H–V model and long-term (17 days) measurements.  相似文献